The objective of this proposal is to better understand the characteristics of the stable hypertrophied myocardium subsequent to pressure and/or volume overloading, as encountered in the course of many correctable lesions, to ventricle and the response to specific cardioactive drugs and to study the scintigraphic characteristics and quantitation of right ventricular and left ventricular hypertrophy. A major thrust will be systematic investigation of alterations in myocardial function during stable hypertrophy and in regression of hypertrophy following relief of the overload as well as in the transition of hypertrophy to failure. The long-term goal is to improve understanding of the pathophysiology of cardiac disease and the treatment of patients suffering from it. Work will be divided into several closely interrelated component areas: 1. Physiological and biochemical characteristics of hypertrophy. a. Segmental and global LV function in hypertrophy; relation to type of hypertrophy. b. Effects of ischemia on global and segmental LV function in hypertrophy. c. Comparison of the characteristics of the volume-overloaded and pressure overloaded pumping chamber; role of the pericardium in coupling of the right and left ventricles. d. Effect of stress on regional myocardial blood flow distribution and other characteritics in LVH and RVH: studies with hydrogen polarography. e. Response of the hypertrophied heart to drugs - ATP, norepinephrine and nitroprusside. 2. Quantitation of hypertrophy by scintigraphic radionulcide imaging methods, RVH and LVH. 3. Regression of myocardial hypertrophy. a. Physiological and biochemical characteristics of the regression stage. b. Scintigraphic radionuclide imaging characteristics. 4. Studies of the changes in the mechanism of the transition from hypertrophy to failure. a. Combination of volume and pressure overload. b. Failure developing late in hypertrophy; physiological and scintigraphic changes.